Carburetor



United States Patent Inventor Kenichi Yamamoto Hiroshima-sill, Japan Appl. No. 778,115 Filed Nov. 22, 1968 Patented Dec. 8, 1970 Assignee Toyo Kogyo Kabushiki Kalsha CARBURETOR 2 Claims, 2 Drawing Figs.

U.S. Cl. 123/127, 123/65, 123/73 Int. (I F02m 13/06, F0219 75/02, F0213 33/04 Field ofSearch ..123/7 3 (A3 127, 65

[56] References Cited UNITED STATES PATENTS 2,621,029 12/1952 Moseley l23/127X FOREIGN PATENTS 889,441 2/ 1962 Great Britain 123/127 993,467 5/1965 Great Britain.. 123/127 1,011,934 4/1952 France 123/73 Primary Examiner-Wendell E. Burns Attorney-Sughrue, Rothwell, Mion, Zinn & MacPeak ABSTRACT: In a carburetor for feeding both a fuel and air mixture and lubricating oil to the engine, the lubricating oil is fed to the carburetor by an engine-driven oil pump via a lubricating oil delivery port which opens up into the carburetor air passage upstream of the throttle valve when in closed I position but downstream of the throttle valve when in slightly open position, and circumferentially offset from the slow speed and idling fuel ports.

PATENTEDDEB 8|97U 4 4 3 I INVENTOR KENICHI YAMAMOTO ATTORNEYS.

1 CARBURETOR DESCRIPTION or THE PRIOR ART In two-cycle internal combustion engines and engines of the rotary piston type, it is common to supply lubricating oil to the cylinders, together with the incoming fuel and air mixture. The lubricating oil and the gasoline are atomized and mixed with the combustion air during air passage through the carburetor. The quantity of lubricating oil in such cases increases with an increasing quantity of gasoline during fuel demand. However, during engine idling and engine braking, very little fuel is being supplied and the lubricating oilalso decreases sharply in quantity whereby engine burnout results.

If means are taken to ensure that the proper amount of lubricating oil is fed to the engine through the carburetor during engine braking, an adverse situation results during normal operation in which an unnecessarily large quantity of lubricating oil is deliveredto the engine cylinders. Due to the large consumption of lubricating oil at this time, there is a large increase in carbon within the cylinders.

Therefore, it is sometimes common to isolate the lubricating oil from the gasoline by maintaining both the gasoline and the lubricating oil in different supply tanks. '1 he optimum quantity of lubricating oil for the normal driving condition of the engine is supplied to the carburetor by a lubricating oil pump which supplies a volume of oil to the carburetor in proportion to the speed of the engine and the engine load. The lubricating oil is then atomized in the carburetor and mixed with the inlet combustion air.

However, where the lubricating oil is isolated from the gasoline under such a method, a mixing chamber must be constructed in such a way that the lubricating oil is atomized and mixed with the inlet air. The supply hole or port for the lubricating oil which opens up into the carburetor air passage lies adjacent to the carburetor throttle valve, and with the valve in closed or blocked position, the port or supply hole is located downstream of the throttle valve.

Accordingly, under the prior art practice, during ordinary driving, the throttle valve is open and the lubricating oil is therefore supplied of optimum quantity, determined by lubricating oil pump rotation, and excellent results are obtained. But, during engine braking, with the throttle valve closed or nearly closed, there results a large negative pressure being produced inside the carburetor passage, downstream of the throttle valve. The engine braking condition occurs during vehicle operations in which the engine is actually being driven through the gear train by the inertia of the moving vehicle. In such a case, the lubricating oil which is carried in the passageway between the lubricating oilpump and the supply port for the lubricating oil within the carburetor air passage, is rapidly sucked from this passageway by the negative pressure existing in the carburetor air passage downstream of the throttle valve. Consequently, a larger quantity of lubricating oil than is necessary is mixed with the inlet air.

Further, since the oil passageway is empty of lubricating oil when the throttle valve is suddenly opened, from such an engine-braking state a condition exists at this point in which an insuff cient amount of lubricating oil is momentarily supplied,

until the engine lubricating oil pump refills the passageway. Thus, the prior art design has not always been able to supply the optimum quantity of lubricating oil to the engine cylinders during all phases of engine operation under conditions in i which the lubricating oil is atomized and mixed with the inlet air in the carburetor air passage, notwithstanding the fact that an optimum quantity of lubricating oil is being measured and supplied to the carburetor oil inlet port by the engine-driven lubricating oil pump.

I SUMMARY OF THE INVENTION 7 The present invention involves the concept of feeding the optimum quantity of lubricating oil as measured by alubricating oil pump driven by the engine, by mixing the same with en- 'gardless of the position of the throttle valve within the carburetor air passage.

Specifically, the inverition has application to an internal combustion engine which incorporates a carburetor for mixing fuel and air and delivering the mixture to the engine cylinders. A throttle valve controls the mixture and a lubricating oil port opens up into the air passage adjacent the throttle valve and is connected to a lubricating oil supply having an engine operated lubricating oil pump for delivering lubricating oil at a rate proportional to engine speed. The lubricating oil port is positioned such that it lies upstream of the throttle valve when the throttle valve is in closed position and on the downstream side of the throttle valve when the throttle valve is slightly open to ensure proper mixing of atomized lubricating oil with the intake air during all conditions of engine operation. Preferably, for a carburetor which includes a slow speed fuel port and/or an idling fuel port within the carburetor passage, the lubricating oil port is circumferentially offset from these two ports, which are normally downstream thereof.

BRIEF DESCRIPTION OE THE DRAWINGS FIG. 1 is a side elevation, in section, of a carburetor for use with a two-cycle engine and modified in accordance with the principles of the present invention.

, FIG. 2 is a front elevational view of the carburetor shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, a carburetor construction incorporates a carburetor body 1 of conventional form which communicates at its upper end, with an air cleaner (not shown) and whose lower end may be readily coupled to the inlet or intake manifold for an engine, such as a two-cycle internal combustion engine (not shown). The carburetor body further carries a float chamber 2 of typical construction which carries a mass of fuel 13 in liquid form whose level is controlled by float 14 in conventional fashion. An air passage 15 includes, at its upper end, a Venturi passage section 4 of reduced diameter which opens up in the vicinity of throttle 5 to form a cylindrical .air intake passage 3 which is coupled to the engine manifold (not shown). A pivotal throttle valve 5, in conventional fashion, controls the volume of air. passing through air passage 15. A main fuel jet 6 is carried within the airpassage 15 of the carburetor within the Venturi and communicates with the float chamber 2. Further fuel passages couple the float chamber 2 to conventional slow speed port 7 and slowidling port 8, these ports opening up into the cylindrical portion 3 of the air passage near the throttle valve 5. A common fuel line connects ports 7 and 8 to the supply of fuel 13 in the float chamber 2 with a continuation of this passage forming air bleed 9. In these respects, the carburetor is conventional.

Further, there is schematically illustrated a lubricating oil pump 10 which is coupled, as indicated by the dotted line, to a lubricating oil supply passage or passageway 12 carried by the carburetor body 1. The passage 12 opens up into the air passage 15 of the carburetor through a lubricating oil carburetor inlet port or supply hole 11. Unlike the prior art carburetors, the inlet port 11 for the lubricating oil is positioned adjacent the throttle valve 5 at such a position that it lies on the upstream side of the throttle valve when the throttle valve is in closed position and on the downstream side of the throttle valve when the valve is slightly open and in addition, as indicated in FIG. 2, the lubricating oil port '11 is circumferentially shifted and above the vertically alined slow-idling port 8 and slow speed port 7. By being circumferentially shifted in this manner, in case the viscosity of the lubricating oil increases as it would during cool starting, or if a lubricating oil of comparatively high viscosity is used, due to its circumferential shift, lubricating oil will not block either slow speed port 7 or slow-idling port 8 in case a film of oil flows gine intake air in proper quantities under all conditions redownwardly along the sidewall of cylindrical casing section 3.

The carburetor of the present invention is so constituted that, during normal engine operation, the lubricating oil pump 10 supplies the optimum quantity of oil in accordance with the number of engine revolutions and engine loading. The enginelubricating oil then spouts from the supply hole or port 11 and readily mixes with the inlet air passing through air passage 15 which is moving at relatively high velocity and thus, the optimum quantity of lubricating oil is supplied to the engine.

During idling and engine braking, the throttle valve 5 moves to nearly closed position, as indicated, and a large negative pressure is produced in the inlet cylinder 3 downstream of the throttle valve 5. Since the supply hole or port 11 for the lubricating oil is positioned above the now closed throttle valve 5, this negative pressure does not act upon supply hole or port 11 due to the presence of the closed throttle valve 5. 15

Under such driving conditions, again the optimum quantity of lubricating oil spouts from the supply hole or port 11 into the intake passage portion 3 under the action of the positive pressure pump 10 and is mixed with the inlet air of relatively large velocity which flows through the small gaps existing on either side of the closed throttle valve 5. Accordingly, under such driving conditions, an excessive quantity of oil is never supplied to the engine. Moreover, in the case of an abrupt acceleration, after valve closure, as a result of idling or engine braking, the passage 12 carrying the lubricating oil is always filled with oil so that the lubricating oil may be immediately supplied to the inlet air in proportion to the size of the aperture existing between the throttle valve 5 and the air passage wall, and under the provisions of the present invention, there will be no temporary shortage of lubricating oil. With the throttle in closed, or nearly closed condition, the lubricating oil, which is measured at the optimum quantity by the enginedriven pump 10, flows from the supply hole or port 11 into the carburetor under the pure discharge pressure of the lubricating oil pump for atomization and mixing with the incoming air by dynamic effect of inlet'air passing through the narrow gap between the throttle valve and the inside wall of the carburetor air passage.

From the above description, it is evident that under the modified carburetor of the present invention, the engine is always able to supply the optimum quantity of lubricating oil regardless of the driving conditions of the engine driven vehicle.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in the form and details may be made therein without departing from the spirit and scope of the invention.

I claim:

1. In an internal combustion engine including:

a. a carburetor having an air passage, a Venturi therein for controlling the mixture of atomized fuel and air, a throttle valve carried by said air passage, and a lubricating oil port opening up into said air passage;

b. lubricating oil under storage;

c. an engine operated pump for pumping the lubricating oil from said oil storage to said oil port at a rate proportional to engine speed, the improvement wherein; and

d. said lubricating oil port is positioned adjacent to said throttle valve at such a position that it lies upstream of said throttle valve when said throttle valve is in closed position, and downstream of said throttle valve when said throttle valve is slightly open.

2. The internal combustion engine as claimed in claim 1 wherein: said carburetor air passage includes a slow speed fuel port and an idling fuel port and wherein said lubricating oil port is circumferentially offset therefrom. 

